v0.24.0 — Live backdrops & scroll-reveal motion

The gate for SPEC-104: teach bg to host a live sandbox as a bare, presentational, full-bleed backdrop. Covers §1–§4 — the constrained body, the engine relocation that mirrors bg-video, the bare-surface guardrail, and boot-frame layering. Everything downstream (the preset, the showcase) builds on the data-bg-guest contract this establishes.

SPEC-104 §5: make a reusable sandbox backdrop applicable by name (bg="midnight-waves") like any other preset, by adding a sandbox descriptor to BgPresetDefinition — resolved at transform time (not the identity engine, which has no file access), expanding into the WORK-428 data-bg-guest body.

SPEC-104 §6 + docs: document the bg guest body, the bare-surface guardrail, the sandbox preset (with the refrakt.config.json example), and the boot-frame layering; ship the music-blog backdrop pattern as a working showcase exercising the layout-cascade + SPEC-006 audio-bridge composition.

The gate for SPEC-105 (§1–§3): a shared, closed reveal modifier plus an orthogonal stagger modifier on section-level runes, emitting the generic data-* hooks and the per-child index the motion CSS and behaviour read. Pure intent → attributes; no look here.

SPEC-105 §4: a single dimensions/motion.css + motion tokens that render each reveal character — covering all section runes from one stylesheet, with the transform-composition and global-hook rules that keep it from becoming per-rune work.

SPEC-105 §5–§6: the timing trigger and the no-JS/SSR safety. A tiny IntersectionObserver behaviour flips data-in-view; enhancement gating guarantees the static page is always complete. JS = when, CSS = how.

SPEC-105 §7 + docs: a theme-authoring motion dimension page and an author-facing reveal/stagger reference, plus a feature-stagger demonstration.